Carcinoma of Unknown Primary—Patient Version

Overview

Cancer of unknown primary is a rare disease in which cancer cells have spread in the body but the place the primary cancer began is unknown.

There are a number of reasons why the primary cancer may not be found. The primary tumor may be too small to find, or the body’s immune system may have already destroyed it. It’s also possible that the primary tumor was removed during surgery for another condition and doctors didn’t know the cancer was there.

A physical exam and tests and procedures are done to try to find the primary tumor. It is important to know the type of cancer so the best treatments for that type of cancer can be used. If the primary tumor is found, treatment is based on that type of cancer.

If the primary tumor cannot be found, treatment is based on what the doctors can learn about the cancer cells. Important information may include the place in the body where the cancer cells were found, the type of cancer cell, and how different the cancer cells are from normal cells. Signs and symptoms caused by the cancer of unknown primary, and the results of the tests and procedures, are also used to plan treatment.

Since cancer of unknown primary is cancer that has already spread in the body, current treatments often do not cure the cancer.